Mechanics from Spain and the Philippines are being transferred to Ireland to try to clear NCT delays.
The Road Safety Authority says drivers are waiting an average of nearly 25 days to get an appointment - up from less than 12 days in 2020.
Covid and staff shortages are being blamed, with some motorists experiencing delays of nearly six months for the test.
The Road Safety Authority is before the Oireachtas Transport Committee on Wednesday to answer questions on the backlog.
Committee chairman Kieran O'Donnell says drivers are worried about breaking the law.
"People are, through no fault of their own, being forced to drive cars without an NCT test being in date.
"[They are] possibly being stopped by the guards, who are taking a pragmatic view so long as you have applied for an NCT test."
"The insurance companies are the same, but that's strictly in terms of a pragmatic view.
"It's not within in the strict terms of the law," Mr O'Donnell said.
